1. Field of the invention
The present invention concerns flywheels for transmission systems, of the kind usually constituting an inertial member in clutches, especially clutches designed to be fitted to automobile vehicles.
It is more particularly directed to flywheels, known as damper-type flywheels, incorporating damper means operative against possible torsional torques.
2. Description of the prior art
It is usual to incorporate a torsional damper device in a transmission system to filter out vibration that can arise anywhere in the kinematic system that the transmission constitutes, extending from the motor to the wheel axles in the case of an automobile vehicle.
The torsional damper device is usually incorporated in the friction disk of the clutch.
However, it has also been proposed to incorporate a torsional damper device in the flywheel, either instead of or in conjunction with the damper device in the friction disk, for certain applications of a specific kind, in particular for vehicles where the motor develops a relatively high torque at low rotation speeds, where there may be a particular requirement to eliminate "trash" noise which occurs under load.
This is the case, for example, with the damper-type flywheel that is the subject matter of German Pat. No. 29 31 423.
Generally speaking, a damper-type flywheel of this kind comprises two coaxial parts disposed to rotate relative to each other, namely a first part comprising two spaced annular flanges and a second part comprising at least one annular flange, there being two in practice, disposed between the flanges on the first part, together with spring means operative between the first and second parts and comprising circumferentially acting spring members individually accommodated in openings provided for them in the flanges of the first part and with which cooperate arms forming part of the flange or flanges of the second part.
In the embodiments proposed there is circumferential clearance, in the inoperative configuration of the flywheel, between the circumferentially acting spring members and the arms on the flange or flanges of the second part that have to interfere with them, so that these circumferentially acting spring members are not operative for lower values of relative angular displacement between the two parts but only for higher values of such displacement, only friction means provided axially between said parts being operative for said lower values of relative angular displacement.
This arrangement has advantages, in particular that of simplicity.
However, it also has the disadvantage of entailing, in the inoperative configuration of the flywheel, uncertainty as to the angular position of the flange or flanges of the second part relative to the flanges of the first part, this angular position merely corresponding to that at the time the torque to be transmitted from one of said parts to the other drops below the friction torque between them at this time.
Because of this uncertainty as to the position of the flange or flanges of the second part, the circumferential clearance provided between the arms of this flange or flanges and the circumferentially acting spring members with which these arms have to interfere is distributed in an uncontroled manner, and thus almost inevitably in an irregular manner, between the two circumferential directions, with the possibility of there remaining no clearance for one circumferential direction, to the detriment of the overall functioning.
Also, given these conditions the arms of the flange or flanges of the second part come into circumferential contact with the circumferentially acting spring members with which they have to interfere or with members disposed between them and the latter with some violence, inevitably generating noise.
To alleviate these disadvantages consideration might be given to providing between the two parts of a damper-type flywheel of this kind spring centering means so that, for the inoperative configuration of the flywheel, there is circumferential clearance in both circumferential directions between the circumferentially acting spring members operative circumferentially between said parts and the arms of the flange or flanges of the second of said parts designed to interfere with the latter.
However, the problem is then to provide a simple means of fitting these spring centering members without this having any other consequences with regard to overall functioning, and even though the space into which they have to be fitted is already particularly congested.
A general objective of the present invention is a device providing a satisfactory solution to this two-fold requirement.